1Biomedical
and Metabolic Imaging Branch, NIH/NIDDK, Bethesda, MD, United States

Single volume 1H-MRS can be used to measure
human liver glycogen in vivo, but various factors could lead to quantitation
errors. T1 and T2 relaxation effects were examined on
glycogen phantoms with ionic strength, pH and temperature mimicking the
intracellular environment of the liver using the same PRESS sequence and
parameters used for in-vivo measurements of glycogen in humans. Signal
variations as a function of echo time (TE) and echo spacing with a fixed TE
showed effects of homonuclear coupling. Thus, assuming an exponential model
to correct glycogen signals for relaxation could lead to an underestimation
of the glycogen concentrations.